Trying to understand Domain Participant Listeners and what discovery implies

[KansaiUser]

I am reading the documentation trying to understand FastDDS.

When talking about Domain Participants (and specifically Domain Participant Listeners) what is exactly meant when saying "a Publisher has been 'discovered'"?

In the documentation it says

on_publisher_discovery(): A new Publisher is discovered in the same domain, a previously known Publisher has been removed, or some Publisher has changed its QoS.

What does "being discovered" implies?

Does it indicate that a publisher has been detected as started publishing topics? or just that there is a publisher (even though it never publishes nothing yet)

I suspect it is the former although just by reading the docs it would suggest the latter

• Is there a way to find the active (being published) topics?
• With on_publisher_discovery` I can see the discovered topics but can I see who is publishing it?

Thanks a lot